島根県益田市の中部中新統益田層群から産出したCallianassa nishikawai Karasawa,1993の頭胸甲の化石

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The carapace of Miocene species Callianassa nishikawai Karasawa，1993 is first described from the Middle Miocene Toyoda Formation，Masuda Group in Masuda City，Shimane Prefecture，southwestern Japan．It represents following characters：dorsal carapace longer than wide；rostral spine triangular with an obtuse apex；two lateral projections smaller than rostral spine；dorsal oval extending about 0.3 of carapace length；cervical groove distinct; cardiac region narrow without cardiac prominence，which could not be found in the type specimens．In this paper，the systematic status of C. nishikawai Karasawa，1993 is reexamined on the basis of their characters．C. nishikawai is placed in the family Callianassidae Dana，1852 and readily distinguished from the subfamily Eucalliinae Manning and Felder，1991 in the Callianassidae．